CDKN1A and urinary bladder cancer: Of interest is that in human bladder cancer, cyclin D1 (CCND1) is amplified in 20%, whereas inactivating mutations, hemizygous and homozygous deletions of the tumor suppressor CDKN1A gene that encodes p21CIP/WAF1 have been recently reported with higher frequencies of deletion in muscle invasive (MI) disease [44].